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Automated tiered storage (ATS) automatically moves data residing in one class of disks to a more appropriate class of disks based on data-access patterns, with no manual configuration necessary. Frequently accessed, hot data can move to disks with higher performance, while infrequently accessed, cool data can move to disks with lower performance and lower costs.
Each virtual disk group, depending on the type of disks it uses, is automatically assigned to one of the following tiers:
Performance: This highest tier uses SSDs, providing the best performance but also the highest cost.
Standard: This middle tier uses enterprise-class SAS hard drives, which provide good performance with mid-level cost and capacity.
Archive: This lowest tier uses nearline SAS hard drives, which provide the lowest performance with the lowest cost and highest capacity.
A volume’s tier affinity setting enables tuning the tier-migration algorithm when creating or modifying the volume so that the volume data automatically moves to a specific tier, if possible. If space is not available in a volume's preferred tier, another tier will be used. There are three volume tier affinity settings:
No affinity: This is the default setting. It uses the highest available performing tiers first and only uses the archive tier when space is exhausted in the other tiers. Volume data swaps into higher-performing tiers based on frequency of access and tier space availability.
Archive: This setting prioritizes the volume data to the lowest-performing tier available. Volume data can move to higher-performing tiers based on frequency of access and available space in the tiers.
Performance: This setting prioritizes volume data to the higher-performing tiers. If no space is available, lower-performing tier space is used. Performance-affinity volume data swaps into higher tiers based on frequency of access or when space is available.